The objective of this grant is to develop statistical methods and models useful for epidemiological studies with cross-sectional sampling designs. The proposed research is focused on (1) statistical analysis of prevalent cohort data in prospective studies, (2) statistical analysis of cross-sectional data in retrospective studies, and (3) development of stochastic epidemic models for the study of epidemiological theory and statistical inference. The major topics include nonparametric and semiparametric methods for a variety of statistical problems. In particular, statistical methods and theory for one-sample estimation, two-sample testing and regression procedures will be developed.